Battery systems have been widely exploited in various electric vehicles, uninterrupted power systems, and related energy storage devices. The battery management system (BMS), which is the key component of the battery and products of different applications, is mainly employed to improve the utilization of the battery, to prevent the battery over-charging and over-discharging, to extend the battery life, and to monitor the battery status.
As the development of the battery management system progresses, the following functions can be implemented at present. (1) Accurate estimation of SOC: the state of charge (SOC) of the battery set, that is, the remaining battery capacity, can be accurately estimated, so as to ensure that the SOC is maintained within a reasonable range and to prevent damage to the battery due to over-charging or over-discharging. (2) Dynamic monitoring: in the process of battery charging and discharging, the terminal voltage, temperature, charging and discharging current and total battery voltage of each battery in the battery set are collected instantaneously so as to prevent battery over-charging or over-discharging. Meanwhile, it is able to promptly determine the battery in question so as to maintain the reliability and efficiency of the entire battery set. (3) Battery balance: it is to enable each battery in the battery set to reach a balanced state of charge. Balance technology is the key technology of a battery energy management system that is being researched and developed in the world at present.
In Taiwan patent No. 1527341, a battery management system, a current balancing method, and a circuit are disclosed. The battery management system includes: a battery set including a plurality of battery modules; and a plurality of control circuits corresponding to the plurality of battery modules. Each of the control circuits includes: a control unit that manages a corresponding plurality of battery modules and is operated by a corresponding consumption current; and a compensation unit, coupled to the control unit and configured to generate a corresponding compensation current such that the sum of the corresponding consumption current and the corresponding compensation current equals a target total current. The control circuits at least include a first control circuit and a second control circuit. The first control circuit includes a first control unit operated with a first consumption current. The second control circuit includes a second control unit operating with a second consumption current. The first control circuit generates a first compensation current based on the comparison of the first consumption current and the second consumption current. The second control circuit generates a second compensation current based on the comparison of the first consumption current and the second consumption current.
However, regarding practical application and mass production of a battery management system circuit, there are many problems that need to be overcome in the conventional art. Taking the aforementioned patent as an example, a battery management system and a power supply circuit are integrated and fabricated on a single circuit board. The amount of output current is limited to the current amount of the battery management system and a stable output of high current cannot be provided. Thus, the applicability of the product is reduced. The constant voltage charging method provides a constant voltage to charge the battery from the beginning to the end of charging. In the beginning of charging the battery, the charging voltage is greater than the battery voltage. The battery produces high current, so the sudden rise in temperature occurs in the battery. As the battery capacity increases, the battery voltage will be close to the voltage provided by the charger. At this situation, the charging time increases although the internal current of the battery is reduced.